Here is the issue. All OBDII communications must go through the CAN gateway. The CAN gateway can only handle one instruction at a time. It is possible to plug 2 devices into the connector with a "Y" cable. However, there will be problems if both devices try to talk to the car at the exact same time. The CAN gateway has no way to know that there are 2 devices, so it cannot address only one to send data to only one device. As long as one of the 2 devices is relatively quiet (not constantly demanding info), both devices will probably work OK. However, if one of the devices is polling for data constantly (like the Torque App running 6 gauges), I would not expect any other device to reliably communicate.
In other words, 2 devices can be plugged in at the same time, but they might not both work as intended. For any important function, I would not recommend plugging 2 devices in at the same time.
Have Fun!
Don